1. Field of the Invention
The present invention relates to an angular velocity sensor suitable for use in detecting an angular velocity of, for example, a rotator.
2. Description of the Related Art
An angular velocity sensor is generally known, which comprises a substrate, an oscillator displaceably supported by the substrate via an oscillator-support beam in two directions orthogonal to each other, oscillation-generating means for oscillating the oscillator in one of two directions parallel to the substrate (i.e., an X-axis direction or a Y-axis direction), and an angular-velocity detecting means for detecting the displacement of the oscillator as an angular velocity when the oscillator is displaced in the other of the two directions (Japanese Unexamined Patent Application Publication No. 11-325915, for example).
If, while an oscillation about the X axis, for example, is provided to the oscillator, and an angular velocity about a Z axis orthogonal to X and Y axes is applied from the exterior, a Coriolis force (inertial force) acts upon the oscillator and causes the oscillator to be displaced in the Y axis direction. The angular-velocity detecting means detects the displacement of the oscillator in the Y axis direction due to the Coriolis force as changes in an output or in static capacity of a piezoelectric body, etc.
In a conventional technique, a frame-shaped member surrounding the oscillator is provided on the substrate, and by supporting the oscillator with the frame-shaped member via an oscillator-support beam, the effect on the oscillator by changes in the characteristics of the oscillator-support beam, etc., due to temperature changes is reduced so as to stabilize the oscillating state, resulting in improving detection accuracies.
In the above-mentioned conventional technique, by maintaining the oscillator in a stabilized oscillating condition relative to the X axis direction, a displacement of the oscillator when it is displaced in the Y axis direction due to a Coriolis force is detected as an angular velocity.
However, not only an angular velocity may be applied from a rotator attached thereto, etc., but also an eternal force may be applied to the rotator, or an inertial force due to changes in movement may be applied thereto, with an impact which is then applied to the oscillator via the oscillator-support beam, etc.
In this case, when waveforms of the impact include an oscillation having a frequency close to a resonant frequency of the oscillator, the oscillator may resonate sufficiently due to the impact so that the oscillating state becomes unstable or the oscillator is displaced in the detecting direction regardless of the Coriolis force.
Therefore, the conventional technique has a problem that when an impact is applied from the exterior, changes in detecting sensitivity for an angular velocity and errors in detecting values are prone to occur, resulting in degrading of the reliability as a sensor.
Also, in the conventional technique, the frame-shaped member for supporting the oscillator is provided on the substrate; however, the frame-shaped member only serves to reduce the effect due to temperature changes and it does not abate the impact transmitted to the oscillator from the substrate.